Recorder Functions
Q: What is the difference between peak-to-peak and RMS modes?
A: Peak-to-peak mode is used for both AC and DC signals where the peak values of the waveforms need to be recorded. In RMS mode, the value recorded is the RMS value of the waveform. For example, if you need to record the voltage of an AC outlet, you would use peak-to-peak mode to see the sinusoidal signal and RMS mode to the the RMS voltage value.
Q:What is DSP?
A: DSP is an acronym for "digital signal processor". Many Astro-Med recorders use DSP's for real-time filtering and math functions. For filtering, the DSP emulates a traditional analog filter but gives you the flexibility of choosing your cutoff frequencies> For example, you can easily choose to have a lowpass filter with a cutoff frequency of 40 Hz or a highpass filter at 1 Hz.
Q:How is the timebase that is printed on the chart calculated?
A: The timebase is equal to the inverse of the chart speed. For example, a chart speed of 25 mm/sec is equivalent to a time base of 1/(25mm per second) or 40 msec/mm.
Q:Why does my recorder print a thick black band when I input a fast signal and run the recorder at its highest speed.
A: Most recorders have a maximum chart speed of between 100 and 500 mm/sec. A chart speed of 100 mm/sec gives you a resolution of 10 msec/mm. At this resolution, a 1,000 Hz sine wave will be 0.1 mm wide, making it difficult to resolve any detail from a real-time printout. In order to resolve more detail, use the data capture utility resident in most Astro-Med recorders to capture and playback data with much more resolution.
Recorder Operations
Q:What is the ATTENUATOR setting on my Dash 4u, Dash 8n, Dash 8u or Dash 16u for?
A: In order to minimize noise and maximize precision, there are different ATTENUATE settings in your recorder. This setting limits the maximum input and sensitivity and determines the amount of available OFFSET. The ATTENUATOR setting should be chosen for your signal type, before setting your RANGE and OFFSET.
Q:What are the OFFSET and RANGE settings on my Dash 4u, Dash 8n, Dash 8u, or Dash 16u for?
A: The RANGE setting is used to define the full-scale measurement span for the grid while the OFFSET is used to define the center point of the grid. For example, if you need to measure a signal that ranges from -5VDC to +5VDC, the RANGE should be set to 10V and the OFFSET should be 0V. If you need to measure a signal that ranges from 0VDC to +10VDC, the range should be set to 10 V and the OFFSET should be +5V.
Q:What is the DC/GND setting on my recorder for?
A: This setting chooses whether you want the signal (DC) to be recorded or if you want to see the baseline (GND). The GND setting is often used to determine where your baseline will be and allows you to adjust the OFFSET accordingly. When recording waveforms, this setting should always be DC.
Q:How can I quickly see the current settings in the recorder?
A: Astro-Med recorders have a HELP button which gives you access to many printed status reports. These reports indicate parameters such as analog, data capture, trigger and chart settings. Press the HELP button to get a list of the available reports.
Q: How do I set up a chart format for a specific number of channels on my Dash 4u, Dash 8n, Dash 8u, Dash 10 and Dash 16u?
A: These portable recorders have a built-in utility called Auto-Chart. This is a "wizard-like" function that asks you to specify the number of channels on the chart, whether you want individual or overlapped grids, and if you want text buffers or event markers on the chart. A chart is automatically generated for you. If you need a more customized chart, you can use the MODIFY CHART menus for complete control over the chart output.
Q:How do I calibrate my recorder?
A: Most Astro-Med recorders have either built-in or module-based automatic calibration. By connecting a cable or plugging in a calibration module, you can calibrate your recorder on a channel-by-channel basis. For specific instructions for your particular model, refer to your operations manual.
Trigger Operation and Function
Q:Why does my trigger light stay on constantly?
A: The trigger light is an indication that a trigger setting is being met. When this light stays on constantly, it is usually because of a waveform trigger that is satisfying the trigger levels that are set up for that channel. A common mistake is to set up a waveform trigger channel and ignore the settings of all the other channels that can also cause a trigger. The best way to remedy this is to shut off all of the waveform trigger channels and only turn on the ones that you need to trigger from. You should also check to see if your trigger levels are set correctly.
Q:Why do I get a trigger as soon as I press the ARM button?
A: You probably have the "Auto-Trigger" function turned on. This was designed to cause a trigger as soon as you start a capture by pressing ARM. You can turn Auto-Trigger off in the "SETUP DATA CAPTURE" menu.
Q:How do I use the external trigger on my recorder?
A: Most Astro-Med recorders have a utility port connection for external trigger. This signal is a TTL active low, which means by grounding that line, a trigger is asserted. A ground connection is also provided on the utility port for this purpose. You can also connect this port to another TTL-level control system and assert the external trigger with a TTL low.
Q:How do I set up a waveform trigger?
A: Most Astro-Med recorders have the ability to cause a trigger based on a waveform value. In order to set this up, you must choose which channels can cause a trigger and what levels are for that waveform. Depending on the model of Astro-Med recorder, these levels are specified as a voltage or a percentage of full scale. These settings are found under the SETUP TRIGGER menus. You should also review the trigger section of your operations manual for information specific to your model.
Data Acquisition (Capture)
Q:What is data capture and how do I use it?
A: Data capture is a feature in Astro-Med recorders that allows you to save data to memory (either RAM or hard drive depending on the model that you have). This data can then be played back on the chart, previewed using the screen, or transferred to a PC. When using data capture you usually have to select the sample rate, record size, capture operation and pre-trigger amount for your application. These settings are found in the "SETUP DATA CAPTURE" menu. Trigger settings may also have to be set up if you need to perform a data capture based on some waveform criteria. These settings are found under the "SETUP TRIGGER" menu. The ARM key is used to start a data capture.
Q:I archived my data onto my Zip drive, how do I use my computer to view it?
A: The AstroVIEW C software program allows you to review your data, make measurements using cursors, analyze your data, and convert your data to ASCII, Excel or other formats. This software is available for free on our website
Q:How do I get my data to a computer from my Dash 8n, Dash 8u, Dash 4u, or Dash 16u
A: Depending on the recorder, there are many ways to get data to the PC. All of these units can backup your data capture to a removable ZIP disk which can be brought to a PC that has a ZIP drive. These units have Ethernet connections which can be used with AstroVIEW C software to transfer data to a PC. finally, the Dash 8n, Dash 8u, and Dash 4u have SCSI ports which also can be accessed using AstroVIEW C software on a PC with an SCSI port.
Q:What sample rate should I use for data capture?
A: As a general rule Astro-Med recommends using a sample rate that is equal to ten times the fastest signal that you are capturing to faithfully reproduce the signal. For example, if you are capturing a 1 kHz (1000 Hz) signal, you should set the data capture sample rate to 10 x 1 kHz or 10 kHz.
Q:In data capture, what do the terms sample, kSample and Msample mean?
A: Each data point that is captured by any Astro-Med recorder is called a sample. One kSample is equal to 1,000 samples and one Msample is equal to 1,000,000 samples.
Q:How is the data capture duration determined?
A: The data capture duration is determined by three things: the sample rate per channel, the total record size and the number of channels captured. Use the following formula to calculate the data capture duration: Data Capture Duration = Total Record Size / (sample rate per channel x number of channels). For example, if you are capturing 2 channels at a 1 kHz sample rate per channel and a record size of 2 kSamples, the data capture duration will be 1 second: 2ksamples/(1kHz x 2 channels). For convenience, most Astro-Med systems will calculate this duration for you.
